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Summary

CD138 is a marker used to identify normal or malignant plasma cells with a high level of specificity, but does not discriminate normal from abnormal plasma cells and in some cases expression in myeloma may be low compared with normal plasma cells so sensitivity can be an issue. Abberancy of expression is low, but expression may be seen in lymphoplamacytic or marginal zone lymphomas (only on those cells that have plasma cell differentiation)

Normal expression and function

CD138 is a membrane protein that supports cell adhesion or binds cytokines and chemokines. In the hematopoietic system expression of CD138 is acquired by B lymphocytes as they develop into plasma cells.

Diagnostic role

• Most often CD138 used in conjunction with CD38 to identify plasma cells in the diagnosis or monitoring of myeloma
• There is very little aberrant expression, but neoplastic plasma cells may in some cases have weak, variable, or occasionally undetectable expression
• Expression is also seen cells that have plasmacytic differentiation in lymphoplasmacytoid lymphoma or marginal zone lymphoma

Other useful information

Outside of haematopoiesis CD138 is expressed by squamous epithelium.

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SUMMARY TABLES

Expression: primitive cell types Click (i) on table for additional information
AML	B ALL	Burkitt	T ALL	ETP ALL (i)	MPAL (i)	H.gones (i)
40-80%	80-100%	80-100%	<5%	20-40%	20-40%	80-100%

Notes: The main application is in AML. Aberrant expression is seen in ALL particularly in T-lineage, although it may be less likely in Burkitt lymphoma. CD117 expression can indicate MPAL or ETP-ALL if other markers are consistent.

Expression: mature B cell neoplasms
CLL	MCL	FL	MZL	HCL	DLBCL	LPL	PCL
80-100%	<5%	<5%	5-20%	80-100%	5-20%	5-20%	40-80%

Notes: expression is common but selective in mature B-lymphoproliferative disorders, with expression being rare in MCL and FL

Expression: mature T cell neoplasms
ATLL	CTCL Sezary	T-PLL	T-LGL	NK-LGL
limited	limited	limited	limited	limited

Notes: limited reports are consistent with expression being uncommon in T-lymphoproliferative disorders, but expression has been described in angioimmunoblastic lymphoma

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